Most impressive are the low numbers in Utah and Colorado where there are many high elevation basins that are typically just past peak snowpack in late April. Observations from these states show only a few sites above 50% of average snowpack SWE.
At the Spud Mountain SNOTEL in the San Juan Mountains (10,660 ft), the snowpack was completely gone a few days ago.
The few sites in the San Juan Mountains that are above 50% of average snowpack SWE are all at or above 11,000 ft. At Wolf Creek Summit (11,000 ft), snowpack SWE was running near average through February, when Mother Nature put on the breaks for storms and flicked the warming switch. At this high altitude location, the average peak snowpack SWE occurs around May 1, but this year it appears like they are looking at a late March maximum.
In northern Utah, low elevation locations such as the Parley's Summit SNOTEL (7500 ft) are now snow free.
At higher elevations, the storms between heat waves have enabled the snowpack to cling to a precarious existence, at least on northerly aspects, as illustrated by the Snowbird SNOTEL.
This looks like a good year to plan a backpack or peak-bagging trip in places like the Uintas and Colorado Rockies where in many years snow tends to linger and block high elevation routes well into the summer. Baring a major pattern change, it will be a very early hiking season this year.
In the news today... a study out of Harvard looking at warming trends in the eastern US, found that temps have been warming since the enactment of the Clean Air Act. They claim that particulate matter in the air was masking effects of ozone reduction. Now that particulate matter is being reduced,we are seeing the effects of global warming. Is this bunk? Should we fire up some more coal plants in the valley in an attempt to preserve our low elevation snowpack?
ReplyDeleteMatt - I can't comment specifically on the study you cite above as I haven't read it. That being said, it is well documented that particulate pollution (what scientists call aerosols) has both a direct and indirect cooling effect. The direct effect is from the direct scattering of sunlight back to space - you can see this to some degree with your eye on a hazy day. The indirect effect arises because the pollution affects the properties of clouds - which affects how much sunlight they reflect back to space.
ReplyDeleteNow, just to make this a bit more complicated, some of the pollution from coal combustion is in the form of black carbon. Black carbon can have a warming effect (by increasing solar absorption), and can increase the absorption of sunlight by snow and ice - increasing the melt rate.
Understanding these effects is an important area of ongoing research. It is likely that they have had a net cooling effect on the climate that has partially offset the forcing from increases in greenhouse gas concentrations. For example, the IPCC concluded in 2007 that "it is likely that greenhouse gases alone would have caused more than the observed warming over the last 50 years of the 20th century, with some warming offset by cooling from natural and other anthropogenic factors, notably aerosols, which have a very short residence time in the atmosphere relative to that of well-mixed greenhouse gases (Schwartz, 1993)."
Note that this has only partially offset the warming from greenhouse gases.
The vast majority of warming observed in the past 40 years is in the Arctic. Given that greenhouse gases are essentially uniform around the globe, this suggests to me that most of the warming is due to other factors. It also seems to be primarily a Northern Hemisphere phenomenon. Is it possible that reduction of ice and snow, perhaps due to changes in albedo, is the primary cause of temperature changes instead of the other way around? Perhaps changes in particulates and soot emissions, as well as things like Gobi Desert dust events in the spring season, are some of the major factors?
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